Amplifying systems, especially those incorporating automatic volume or automatic gain control circuits, exhibit finite response times when driven by a stepwise increasing or decreasing signal.
Typically this form of amplifier has a settling time when driven by a transient signal. During such settling time, the output signal can undergo one or more oscillations before finally achieving a stable value.
Traditionally the transient behavior has been observed using conventional oscillographic techniques for display of the output envelope while the input drive signal is derived from a gated signal generator which may also furnish trigger signals to the oscillographic sweep circuity.
Measurement of the transient response or settling time to within preset limits above and below the final amplitude of the envelope has thus been done by analog means using the calibrated sweep and a marked graticule display means of the oscillographic device.
It has been difficult to automate the measurement settling time because of the multiple complexities of the drive signal, the oscillographic sensitivity control and sweep control and unknown transient behavior of the device under test to the test stimulus.